There has been known a method of providing music having sound quality most suitable for a sound field environment in which speakers or the like of an audio system are installed, by measuring frequency characteristics in the sound field environment and adjusting the equalizer of the audio system on the basis of the measured frequency characteristics or by previously correcting output sound in accordance with the sound field.
A maximum-length sequence (m-sequence) code and a time-stretched pulse (TSP) signal are known as measurement signals for measuring frequency characteristics. Examples of a method for measuring the frequency characteristics of the sound field environment using such a measurement signal include a method including recording a measurement signal outputted from a speaker using a microphone installed in the listening position and then Fourier transforming the recorded signal to obtain the frequency characteristics (for example, see Patent Literatures 1, 2). An impulse response may be obtained by obtaining cross-correlation characteristics between an outputted measurement signal and a measurement signal recorded using a microphone while using the outputted measurement signal as a reference.